Hi guys,
Havent been on in a while,
Father in law snapped a lower control arm yesterday, looks like someone had fitted a polybush at some point!
Anyhow, Ive rushed into the job and jacked the corner up and removed the old arm ready for the new one to arrive. Thing is i didnt put vehicle into access mode to deflate the bag first
Now the vehicle is jacked on one side (see pic) can i enter vehicle access mode or is that a bit risky being on jack stands? Would it be better to deflate by loosening the connection on the front valve block (I think its the top one for RHS from memory)
cheers dudes
Joe
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Best Regards
Joe
2005 2.7TDV6 HSE AUTO
7th Jul 2024 8:15 pm
rrhool
Member Since: 28 Aug 2014
Location: Norfolk
Posts: 4470
Yes, Polybush is the issue. Standard bushes by far the best.Richard
D3 SE 2007. Triumph 2.5Pi 1973. Ferguson TEA20 1948.
Discovery 2 4.0 ES 2001- Gone
Discovery 1 300Tdi ES '95 - Gone
Range Rover Classic '79 - Gone
8th Jul 2024 9:25 am
Nasher
Member Since: 07 Mar 2009
Location: Clanfield, North of Pompey - UK
Posts: 2763
Re: Disco 4 Snapped Lower Control Arm
rrhool wrote:
Yes, Polybush is the issue. Standard bushes by far the best.
What makes you say that?
Genuinely interested as I've had lots of success with Polybushes in the past, they transformed my D3. However, I did fit the Red ones, which I believe are a bit softer.
It does look like the bushes fitted were far too tight in the hole expanding it outwards until it failed when load was applied. I wonder if the inside of the arm was cleaned out and the corrosion removed, or if the new hard bushes were just pressed in regardless with a 20tn press.
I also wonder if the bolts were fully torqued up with the suspension in extended mode?
We all know of course not to tighten the bolts until the car is back on it's wheels and the suspension is at normal height.
My money would be on bad workmanship fitting the Polybushes rather than them being unsuitable.
.Heaven doesn't want me, and hell is afraid I'll take over.
8th Jul 2024 9:36 am
rrhool
Member Since: 28 Aug 2014
Location: Norfolk
Posts: 4470
IMO, not all poly bushes are the same. Some brands have taken time and effort to develop a replacement bush that works in the particular situation it's intended for. Others are just cast into a shape that roughly fits the metalwork.
In this example, the compound is probably too hard, so instead of being compliant, it has transferred the forces to the bush tube in a way that the metalwork was not designed for.
I too have used poly bushes in some situations (on a classic car), but I'm confident they were designed for the job.
Disco bushes do fail, but it's a very heavy car, and they dont fail annually. A lot of effort was put into the driveability and NVH, and I think OE rubber bushes are probably better.Richard
D3 SE 2007. Triumph 2.5Pi 1973. Ferguson TEA20 1948.
Discovery 2 4.0 ES 2001- Gone
Discovery 1 300Tdi ES '95 - Gone
Range Rover Classic '79 - Gone
8th Jul 2024 10:37 am
joe27979
Member Since: 11 Oct 2015
Location: UK
Posts: 53
I’ve removed the inner shell arch and cracked the 12mm nut supplying air to the suspension bag.
Some of those arch liner fittings were a bar steward!Best Regards
Joe
2005 2.7TDV6 HSE AUTO
8th Jul 2024 10:57 am
itsaguything
Member Since: 20 Dec 2023
Location: Manotick, On
Posts: 196
Let’s be fair… all bushes wear and eventually fail. Granted, poly bushes will have a longer life. But at what cost? In this case (a common theme, btw) a lower control arm. Perhaps related to the limited movement inherent to a poly bush, on a vehicle demanding more movement??
Though I am baffled, why put poly bushes on an off road vehicle? To each their own.
Have you read the workshop manual section on replacement of the lower arm??2015 LR4 HSE Lux Aintree Green
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